© 2001 by The Society for Integrative and Comparative Biology
Interactions Between Limb Regeneration and Molting in Decapod Crustaceans1
1 Department of Biology, Cell and Molecular Biology Program, and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado 80523
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SYNOPSIS |
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 SYNOPSIS INTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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Molting and regeneration of lost appendages are tightly-coupled, hormonally-regulated processes in decapod crustaceans. Precocious molts are induced by eyestalk ablation, which reduces circulating molt-inhibiting hormone (MIH) and results in an immediate rise in hemolymph ecdysteroids. Precocious molts are also induced by autotomy of 5–8 walking legs; adult land crabs (Gecarcinus lateralis) molt 6–8 wk after multiple leg autotomy (MLA). Autotomy of one or more of the 1° limb buds (LBs) that form after MLA before a critical period interrupts proecdysis until 2° LBs re-regenerate and grow to the approximate size of those lost. Based on these observations, Skinner proposed that limb buds produce two factors that control proecdysial events. Limb Autotomy Factor–Anecdysis (LAFan), produced by 1° LBs when at least five legs are autotomized, stimulates anecdysial animals to enter proecdysis. Limb Autotomy Factor–Proecdysis (LAFpro), produced by 2° LBs in premolt animals when at least one 1° LB is autotomized, inhibits proecdysial processes. Initial characterizations suggest that LAFpro is a MIH-like polypeptide that inhibits the synthesis and secretion of ecdysteroid by the Y-organs.
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INTRODUCTION |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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Molting requires the precise coordination of virtually all major organ systems. During proecdysis, as the animal prepares to molt (ecdysis), lost limbs are regenerated, claw muscles atrophy, and the old exoskeleton is partially broken down and resorbed while a new exoskeleton is synthesized underneath (reviewed in Skinner, 1985
; Skinner et al., 1992; Mykles, 1992; Hopkins, 1993; Roer and Dillaman, 1993; Wheatly, 1996). Calcium from the old exoskeleton is stored in gastroliths secreted by the stomach epithelium and/or in calcareous concretions within epithelial cells of the digestive gland (Mykles, 1980; Skinner et al., 1992; Wheatly, 1996). At ecdysis, the animal sheds the old exoskeleton while absorbing large quantities of water to stretch the new exoskeleton (Bliss et al., 1966; Mykles, 1980). During subsequent metecdysis, the synthesis and calcification of the new exoskeleton is completed and claw muscles are restored (Skinner, 1962, 1966).
Molting in decapod crustaceans is controlled by the X-organ/sinus gland complex, which is located within the eyestalks and secretes a peptide hormone, molt-inhibiting hormone (MIH), that inhibits ecdysone production by a pair of Y-organs located in the cephalothorax (Fig. 1). Thus, molting is induced by a reduction in MIH in the hemolymph, which stimulates the Y-organs to synthesize and secrete ecdysone. Ecdysone is then converted to the active molting hormone, 20-hydroxyecdysone (20-HE), by peripheral tissues (reviewed in Skinner, 1985; Chang, 1997).
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Decapod crustaceans readily autotomize their walking legs and claws in response to injury or predation; lost appendages are regenerated before the next molt (reviewed in Skinner, 1985
; Hopkins, 1993). Thus, limb regeneration and molting are obligatorily linked. Limb regeneration is divided into two distinct phases: (a) basal growth or regeneration, which can occur at any time during the intermolt cycle, involves primarily cell division and differentiation and results in the formation of basal papillae and (b) proecdysial growth, which is restricted to the proecdysial period (mostly D0), involves primarily protein synthesis and water uptake and is under hormonal control (Hopkins, 1993). In fiddler crab, exposure to 20-HE is essential for the proecdysial growth phase (Hopkins, 1989). Regenerating limbs provide an external (and therefore noninvasive) measure, defined as the regeneration index [R index = length of limb regenerate x 100/carapace width (Bliss et al., 1966)], of the progress of proecdysial events; in land crabs (Gecarcinus lateralis), the R index increases from 0 to a maximum of 22–24 just before ecdysis (Holland and Skinner, 1976; Skinner and Graham, 1970, 1972). Here I review the interaction between molting and limb regeneration and the characterization of factor(s) that regulate these processes in decapod crustaceans. Related work on insects is also discussed.
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LIMB REGENERATION AND MOLTING |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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Autotomy of one or more limb regenerates (LBA) or walking legs during proecdysis (R index = 7 to 17) delays ecdysis 2–3 wk so that 2° limbs can be regenerated before the next molt (Holland and Skinner, 1976
; Skinner and Graham, 1972) (Fig. 2). LBA causes slowing (at R = 7–10) or complete cessation (at R = 10–17) of growth of remaining 1° LBs, as measured by R index and DNA synthesis, until 2° LBs approach the size of autotomized buds (Holland and Skinner, 1976). The inhibition of proecdysial growth in 1° LBs occurs immediately after LBA, suggesting that severing of the thoracic nerve is the proximal event that leads to suppression of molting. Suppression continues as 2° LBs undergo basal and proecdysial growth until they are nearly the same size as the autotomized 1° LBs.
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LBA inhibits various proecdysial processes that require elevated circulating ecdysteroid in the hemolymph. In addition to suppression of 1° LB proecdysial growth, LBA also delays gastrolith deposition and exoskeleton synthesis (McCarthy and Skinner, 1977
). This suggests that LBA induces a rapid reduction in hemolymph ecdysteroid concentration. As expected, ecdysteroid drops to anecdysial levels immediately after LBA (R index approximately 15) and remains low during basal regeneration; ecdysteroid titers begin to increase during the subsequent growth of the 2° LB (McCarthy and Skinner, 1977; Yu et al., 1999). Primary regenerates removed later in proecdysis (at R = 17–24) are not re-regenerated and the animal molts without the full complement of appendages (Holland and Skinner, 1976). In this case, hemolymph ecdysteroid levels remain elevated (McCarthy and Skinner, 1977; Yu et al., 1999).
The response of 1° LBs to LBA in eyestalk-ligated animals is similar to that in intact animals (Holland and Skinner, 1976; McCarthy and Skinner, 1977). This excludes the possibility that growth inhibition is mediated by factors produced by eyestalk neurosecretory centers, such as MIH or limb growth-inhibiting factor (LGIF) (reviewed in Skinner, 1985; Chang, 1993, 1997; Chang et al., 1993; De Kleijn and Van Herp, 1995). MIH is a neuropeptide of about 8–9 kDa (71–78 amino acid residues, depending on species) that inhibits synthesis and secretion of ecdysone by the Y-organs (Lacombe et al., 1999). LGIF inhibits limb bud growth in land crabs at concentrations that have no effect on molting and thus appears to be distinct from MIH and LAFpro (see below and Hopkins et al., 1979). LGIF appears to be a small peptide, since it is heat-stable, degraded by protease, and is retarded on a G-25 Sephadex gel filtration column (Mr approximately 1 kDa) (Hopkins et al., 1979).
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CHARACTERIZATION OF LAFPRO |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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Extracts of 2° LBs suspend molting, whereas extracts of 1° LBs do not. Extracts of 1° or 2° LBs (R = 12 to 15) were injected into proecdysial land crabs with eight 1° LBs (R = 13–15). Each crab received three injections containing about two LB equivalents at 2-day intervals. Growth of 1° LBs stopped immediately after the first injection of 2° LB extract and remained depressed until 2–5 days after the third and final injection (Yu and Mykles, 1998
; Yu et al., 1999). The average 1° LB growth rates during the week before and during the week after the first injection of either 1° or 2° LB extracts were measured. Secondary LB extract significantly reduced 1° LB growth 65% (P < 0.019). Primary LB extract had no effect on 1° LB growth. These data provide strong evidence that 2° LBs contain a factor, LAFpro, that has the same effect as LBA on proecdysial animals.
The decrease in circulating ecdysteroids by LBA suggest that LAFpro is a MIH-like peptide. The properties of MIH and LAFpro are compared in Table 1. Since MIH/CHH neuropeptides are resistant to heat denaturation, the stability of LAFpro was determined by incubating 2° LB extracts in a boiling water bath for 15 min. Denatured protein was removed by centrifugation and the supernatant fraction was tested for molt-inhibitory activity. The boiled preparation retained inhibitory activity, since growth of 1° LBs was suppressed when it was injected into proecdysial animals (Yu et al., 1999). We then incubated the heat-treated supernatant with proteinase K, which destroyed the molt-inhibitory activity. Boiling the LB extract in 0.1 M acetic acid for 15 min also destroyed the activity. This distinguishes LAFpro from MIH, since MIH is resistant to acidic pH. These data suggest that LAFpro is a MIH-like polypeptide. It is not known how the molecular weight of LAFpro compares with that of MIH/CHH or LGIF.
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MIH/CHH IN THE CRUSTACEAN CENTRAL NERVOUS SYSTEM |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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LAFpro is present in 2° LBs, but it may be synthesized elsewhere and then released from the limb regenerate. The X-organ/sinus gland complex in the eyestalk is the primary location for the synthesis and secretion of a variety of neuropeptides including MIH and crustacean hyperglycemic hormone (CHH) (reviewed in Skinner, 1985
; Chang, 1995, 1997). However, the existence of LAFpro challenges the central paradigm in crustacean endocrinology that all proecdysial processes are coordinated by the eyestalk neurosecretory centers. Proecdysis is also suspended by LBA in eyestalk-ablated animals (Holland and Skinner, 1976), showing that factors produced by the X-organ are not required. Additional experiments with eyestalk-ablated lobsters suggest that there are extra-eyestalk sources of MIH/CHH (Snyder and Chang, 1986). Hemolymph MIH/CHH levels drop after 20 days after eyestalk ablation, although significant amounts are detected as long as one year without eyestalks (Chang et al., 1998).
Immunocytochemical studies show that MIH and related neuropeptides are found in various regions of the nervous system. CHH immunoactivity occurs in the brain, thoracic ganglion, and pericardial organs of Carcinus maenas (Keller et al., 1985; Zhang et al., 1997; Dircksen and Heyn, 1998). In lobster, immunocytochemistry has identified a pair neurons in the subesophageal ganglion and a cluster of neurons in each of the thoracic secondary roots that contain MIH/CHH (Chang et al., 1999). The cell bodies are located in the proximal part of secondary roots and send axons out to the periphery and into the thoracic ganglia. The contents in various parts of the nervous system are consistent with immunocytochemistry (Chang et al., 1999). The secondary roots, which include the cell bodies, have high amounts, whereas the regions that only contain processes have lower amounts. The relatively low content of MIH/CHH in subesophageal ganglia is probably because only two of the hundreds of neurons in the ganglion react with the antibody. The presence of MIH/CHH in the primary root suggests that it contains axons from the secondary root neurons, but the backfilling experiments to establish this have not been done (immunocytochemically-labeled axons cannot be traced after they have entered the ganglion, probably due to limited penetration of antibody). The MIH/CHH neurons in the secondary roots contain electron-dense vesicles characteristic of neurosecretory cells (Livingstone et al., 1981). Depolarization with high K+ stimulates release of MIH/CHH in the medium (Chang et al., 1999). Both octopamine and serotonin inhibit bursting activity, suggesting that neurosecretion is controled by these neuromodulators (Konishi and Kravitz, 1978; Kravitz et al., 1983).
Our working model is that LAFpro is produced in central neurons that send processes to each appendage via the thoracic nerve. Autotomy of a 1° LB severs these axons, which stimulates the synthesis, transport, and/or release of LAFpro from the developing 2° LB.
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SUSPENSION OF MOLTING IN INSECTS BY TISSUE REGENERATION |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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The interruption of proecdysis by tissue regeneration is not unique to crustaceans. Regeneration of legs, antennae, or imaginal disks delays molting in various insect species (O'Farrell and Stock, 1953
; Pohley, 1959, 1960; Madhaven and Schneiderman, 1969; Kunkel, 1975). In German cockroach (Blatella germanica), regeneration of 1–2 metathoracic legs prolongs the duration of the first instar 1–1.5 days (intact controls molt 5 days post-hatching, while operated animals molt 6–7 days post-hatching) (O'Farrell and Stock, 1953, 1954; Stock and O'Farrell, 1954). Developmental changes in epidermis and fat body are delayed to the same extent, thus maintaining proper temporal spacing of events required for successful exuviation (Kunkel, 1975). As in crustaceans, autotomy must be done before a critical period (about 3 days post-hatching) so that there is sufficient time to regenerate the appendage before the next ecdysis. If a leg is autotomized after the critical period only a basal papilla forms and there is no delay; regeneration occurs during the next instar (O'Farrell and Stock, 1953; Stock and O'Farrell, 1954).
In lepidopterans, extirpation of imaginal wing discs in the final instar delays pupation in order for the larva to regenerate lost tissue (Pohley, 1960; Madhaven and Schneiderman, 1969). The delay is proportional to the amount of tissue that is regenerated: in waxmoth (Galleria mellonella), removal of 1 wing disc delays pupation 5 days; 2 discs, 9 days; and 4 discs 14 days (Madhaven and Schneiderman, 1969). During regeneration, unoperated discs do not grow until the regenerated disc increases to about 75% of the extirpated disc (Madhaven and Schneiderman, 1969). Wing imaginal disc regeneration requires low concentrations of ecdyone, but is inhibited at high concentrations (Madhaven and Schneiderman, 1969). The suspension of proecdysis, however, is not mediated strictly by ecdysone titers; injection of ecdysone into final instar larvae has no effect on the molt delay induced by disc extirpation (Pohley, 1961; Madhaven and Schneiderman, 1969). Madhaven and Schneiderman (1969) proposed that regenerates decrease the effective concentration of ecdysone, either by altering ecdysone metabolism (e.g., increased degradation and/or sequestration) or by changing the responsiveness (e.g., nervous and/or humoral mechanisms) of target tissues to hormone.
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CONCLUDING REMARKS |
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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In summary, the effects of tissue regeneration on molting in insects and crustaceans are similar. In both groups, tissue loss must occur before a critical period to permit regeneration before the next ecdysis and proecdysial processes are suspended during regeneration in order to maintain proper timing of events. These similarities suggest a common regulatory mechanism. Thus, what we learn about the control of molting by limb regeneration in crustaceans may have general application to other arthropod groups.
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ACKNOWLEDGMENTS |
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The author thanks Xiaoli Yu, Courtney Rocheleau, Stefanie Kols, and Laura Baker at Colorado State University and Eva Mulder, Sharon Chang, Art Hertz, and Dr. Ernest S. Chang, Bodega Marine Laboratory for their many contributions to this project. Supported by National Science Foundation (IBN-9723576 and IBN-9904528).
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FOOTNOTES |
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1 From the Symposium Recent Progress in Crustacean Endocrinology: A Symposium in Honour of Million Fingerman presented at the Annual Meeting of the Society for Integrative and Comparative Biology, 4–8 January 2000, at Atlanta, Georgia.
2 E-mail: don{at}lamar.ColoState.edu
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SYNOPSISINTRODUCTIONLIMB REGENERATION AND MOLTINGCHARACTERIZATION OF LAFPROMIH/CHH IN THE CRUSTACEAN...SUSPENSION OF MOLTING IN...CONCLUDING REMARKSReferences |
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Bliss, D. E., S. M. E. Wang, and E. A. Martinez. 1966. Water balance in the land crab, Gecarcinus lateralis, during the intermolt cycle. Amer. Zool, 6:197-212.[Web of Science][Medline]
Chang, E. S. 1993. Comparative endocrinology of molting and reproduction: Insects and crustaceans. Annu. Rev. Entomol, 38:161-180.[Web of Science][Medline]
Chang, E. S. 1995. Physiological and biochemical changes during the molt cycle in decapod crustaceans: An overview. J. Exp. Mar. Biol. Ecol, 193:1-14.[CrossRef]
Chang, E. S. 1997. Chemistry of crustacean hormones that regulate growth and reproduction. In M. Fingerman, R. Nagabhushanam, and M.-F. Thompson (eds.), Recent advances in marine biotechnology, Vol. 1. Endocrinology and reproduction, pp. 163–178. Oxford & IBH Publishing Co., New Delhi.
Chang, E. S., M. J. Bruce, and S. L. Tamone. 1993. Regulation of crustacean molting: A multi-hormonal system. Amer. Zool, 33:324-329.
Chang, E. S., S. A. Chang, B. S. Beltz, and E. A. Kravitz. 1999. Crustacean hyperglycemic hormone in the lobster nervous system: Localization and release from cells in the subesophageal ganglion and thoracic second roots. J. Comp. Neurol, 414:50-56.[CrossRef][Web of Science][Medline]
Chang, E. S., R. Keller, and S. A. Chang. 1998. Quantification of crustacean hyperglycemic hormone by ELISA in hemolymph of the lobster, Homarus americanus, following various stresses. Gen. Comp. Endocrinol, 111:359-366.[CrossRef][Web of Science][Medline]
De Kleijn, D. P. V., and F. Van Herp. 1995. Molecular biology of neurohormone precursors in the eyestalk of Crustacea. Comp. Biochem. Physiol, 112B:573-579.[CrossRef][Medline]
Dircksen, H., and U. Heyn. 1998. Crustacean hyperglycemic hormone-like peptides in crab and locust peripheral intrinsic neurosecretory cells. Ann. NY Acad. Sci, 839:392-394.[CrossRef][Web of Science]
Holland, C. A., and D. M. Skinner. 1976. Interactions between molting and regeneration in the land crab. Biol. Bull, 150:222-240.
Hopkins, P. M. 1989. Ecdysteroids and regeneration in the fiddler crab Uca pugilator. J. Exp. Zool, 252:293-299.[CrossRef]
Hopkins, P. M. 1993. Regeneration of walking legs in the fiddler crab Uca pugilator. Amer. Zool, 33:348-356.
Hopkins, P. M., D. E. Bliss, S. W. Sheehan, and J. R. Boyer. 1979. Limb growth-controlling factors in the crab Gecarcinus lateralis, with special reference to the limb growth-inhibiting factor. Gen. Comp. Endocrinol, 39:192-207.[CrossRef][Web of Science][Medline]
Keller, R., P. P. Jaros, and G. Kegel. 1985. Crustacean hyperglycemic neuropeptides. Amer. Zool, 25:207-221.
Konishi, S., and E. A. Kravitz. 1978. The physiological properties of amine-containing neurons in the lobster nervous system. J. Physiol. (London), 279:215-229.
Kravitz, E. A., B. S. Beltz, S. Glusman, M. F. Goy, R. M. Harris-Warrick, M. F. Johnston, M. S. Livingstone, T. L. Schwarz, and K. K. Siwiki. 1983. Neurohormones and lobsters: Biochemistry to behavior. Trends Neurosci, 6:346-349.
Kunkel, J. G. 1975. Cockroach molting. I. Temporal organization of events during molting cycle of Blattella germanica (L.). Biol. Bull, 148:259-273.
Lacombe, C., P. Grève, and G. Martin. 1999. Overview on the sub-grouping of the crustacean hyperglycemic hormone family. Neuropeptides, 33:71-80.[CrossRef][Web of Science][Medline]
Livingstone, M. S., S. F. Schaeffer, and E. A. Kravitz. 1981. Biochemistry and ultrastructure of serotonergic nerve endings in the lobster: serotonin and octopamine are contained in different nerve endings. J. Neurobiol, 12:27-54.[CrossRef][Web of Science][Medline]
Madhaven, K., and H. A. Schneiderman. 1969. Hormonal control of imaginal disc regeneration in Galleria mellonella (Lepidoptera). Biol. Bull, 137:321-331.
McCarthy, J. F., and D. M. Skinner. 1977. Interruption of proecdysis by autotomy of partially regenerated limbs in the land crab, Gecarcinus lateralis. Dev. Biol, 61:299-310.[CrossRef][Web of Science][Medline]
Mykles, D. L. 1980. The mechanism of fluid absorption at ecdysis in the American lobster, Homarus americanus. J. Exp. Biol, 84:89-101.
Mykles, D. L. 1992. Getting out of a tight squeeze—enzymatic regulation of claw muscle atrophy in molting. Amer. Zool, 32:485-494.
O'Farrell, A. F., and A. Stock. 1953. Regeneration and the moulting cycle in Blattella germanica L. I. Single regeneration initiated during the first instar. Aust. J. Biol. Sci, 6:485-500.[CrossRef][Medline]
O'Farrell, A. F., and A. Stock. 1954. Regeneration and the moulting cycle in Blattella germainica L. III. Successive regeneration of both metathoracic legs. Aust. J. Biol. Sci, 7:525-536.[Medline]
Pohley, H. J. 1959. Experimentelle Beitrage zur Lenkung der Organentwirklung, des Hautungsrhythmus und der Metamorphose bei der Schabe Periplaneta americana L. Roux's Arch. Dev. Biol, 151:323-380.[CrossRef]
Pohley, H. J. 1960. Experimentelle Untersuchungen uber die Steuerung des Hautungsrhythmus bei der Mehlmotte Ephestia kuhniella Zeller. Roux's Arch. Dev. Biol, 152:182-203.
Pohley, H. J. 1961. Interactions between the endocrine system and the developing tissue in Ephestia kuhniella. Roux's Arch. Dev. Biol, 153:443-458.[CrossRef]
Roer, R. D., and R. M. Dillaman. 1993. Molt-related change in integumental structure and function. In M. N. Horst and J. A. Freeman (eds.), The crustacean integument. Morphology and biochemistry, pp. 1–37. CRC Press, Boca Raton.
Skinner, D. M. 1962. The structure and metabolism of a crustacean integumentary tissue during a molt cycle. Biol. Bull, 123:635-647.
Skinner, D. M. 1966. Breakdown and reformation of somatic muscle during the molt cycle of the land crab, Gecarcinus lateralis. J. Exp. Zool, 163:115-124.[CrossRef][Web of Science][Medline]
Skinner, D. M. 1985. Molting and regeneration. In D. E. Bliss and L. H. Mantel (eds.), The biology of Crustacea, pp. 43–146. Academic Press, New York.
Skinner, D. M., and D. E. Graham. 1970. Molting in land crabs: Stimulation by leg removal. Science, 169:383-385.
Skinner, D. M., and D. E. Graham. 1972. Loss of limbs as a stimulus to ecdysis in Brachyura (true crabs). Biol. Bull, 143:222-233.
Skinner, D. M., S. S. Kumari, and J. J. O'Brien. 1992. Proteins of the crustacean exoskeleton. Amer. Zool, 32:470-484.
Snyder, M. J., and E. S. Chang. 1986. Effects of sinus gland extracts on larval molting and ecdysteroid titers of the American lobster, Homarus americanus. Biol. Bull, 170:244-254.
Stock, A., and A. F. O'Farrell. 1954. Regeneration and the moulting cycle in Blattella germainica L. II. Simultaneous regeneration of both metathoracic legs. Aust. J. Biol. Sci, 7:302-307.[Medline]
Wheatly, M. G. 1996. An overview of calcium balance in crustaceans. Physiol. Zool, 69:351-382.
Yu, X. L., and D. L. Mykles. 1998. Secondary limb regenerates contain a factor that suspends molting in the land crab. Amer. Zool, 38:42A.
Yu, X. L., E. S. Chang, and D. L. Mykles. 1999. Characterization of a factor in secondary limb regenerates that suspends molting in the lan crab. Amer. Zool, 39:76A.
Zhang, Q., R. Keller, and H. Dircksen. 1997. Crustacean hyperglycaemic hormone in the nervous system of the primitive crustacean species Daphnia magna and Artemia salina (Crustacea: Branchiopoda). Cell Tissue Res, 287:565-576.[CrossRef][Web of Science][Medline]
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